Conventionally, as shown in FIG. 9, this type of ultrasonic flow meter unit includes, for example, a measurement passage 50 through which a target fluid flows, and a pair of ultrasonic transducers 51, 52 which are placed at an upstream side and a downstream side of the measurement passage 50, respectively, and which are capable of transmitting/receiving an ultrasonic signal. The measurement passage 50 is formed of a resin. Each of the ultrasonic transducers 51, 52 includes a piezoelectric element 53, a terminal 54 through which a voltage is applied to the piezoelectric element 53, and an acoustic matching layer 55 bonded to a transmission-side surface of the terminal 54. Each of the ultrasonic transducers 51, 52 is fastened to an ultrasonic transducer mounting section 56 mounted to the measurement passage 50 via a coating material 57 having an elasticity, thereby constituting an ultrasonic flow meter unit 58 (e.g., see Patent Literature 1).